Tube annealing apparatus and method

ABSTRACT

An apparatus and method for annealing thin-walled metal tubes which comprise a body portion and a tapered shoulder portion which has a relatively thickened wall. The tubes are disposed upon a transport conveyor which rapidly moves tubes through an annealing furnace wherein a first heat source is disposed for maintaining a uniform high temperature within the chamber, and wherein a second heat source comprising a plurality of combustion flame burners are disposed within the chamber along the path of travel of the conveyor. The flame emanating from the second combustible flame burners is directed upon the shoulder portion of the tubes which are passed through the annealing furnace. The tubes are rapidly brought to the annealing temperature without rupture or deformation of the thin-walled tubes.

[ TUBE ANNEALHNG APPARATUS AND METHOD [75] Inventor: ilton H. McCann, Wheeling, W.

[73] Assignee: Wheeling Stamping Company,

Wheeling, W. Va.

22 Filed: 11m. 21, 11971 21 Appl. No.: 210,502

[57] ABSTCT An apparatus and method for annealing thin-walled metal tubes which comprise a body portion and a tapered shoulder portion which has a relatively thickened wall. The tubes are disposed upon a transport conveyor which rapidly moves tubes through an annealing furnace wherein a first heat source is disposed 52 us. 01. 148/13, 148/155 for maintaining a uniform high temperature within the 51 1111. C1 (121d 1/08 chamber, and wherein a Second heat Source p [58] Field at Search 148/3, 13, 13.2, ing a plurality of combustion flame burners are 143/155 posed within the chamber along the path of, travel of the conveyor. The flame emanating from the second 5 Refierences UM combustible flame burners is directed upon the shoul- UNITED STATES PATENTS der portion of the tubes which are passed through the 1 annealing furnace. The tubes are rapidly brought to the annealing temperature without rupture or defor- 314961033 2 1970 Gilbreath 148/13 R of the hm'waned tubes" 5 Claims, 3 Drawing Figures 0O 0O 0 O O 0 0O 0O PATENTED DEC 4 I975 SHEET 1 [IF 2 FIG. I.

FIG. 2.

l5 l6 l5 /9 PATENTED HEB 4 I975 SHEET 2 BF 2 TUBE ANNIEALING APPARATUS AND METHOD BACKGROUND OF THE INVENTION Tubular metallic containers are widely used as packagingcontainers in commerce. It is generally desired that'the tubular metal container have a low temper to facilitate the consumers usage. Most such tubular metal containers are formed of aluminum. The containers are formed typically by impact forming a solid disc of aluminum into the thin-walled tubular member. The impact forming step significantly raises the temper of the metal. It has been the practice to anneal theimpact "formed tubular members at a relatively high temperature for several minutes to render the metal soft and workable. In heating very thin-walled tubes, uneven heating or local overheating can easily result in a rup- "least several minutes to effect the annealing process.

SUMMARY OF THE INVENTION An apparatus and method is provided for rapidly bringing the tubular members to the annealing temperature of the metal without rupture or deformation of the thin-walled tubes. The typical thin-walled metal tubes comprise a uniform diameter body portion and a tapered shoulder portion at one end thereof, which has a relatively thickened-wall. An enclosed heating chamher is provided with an inletand an outlet opening, and a tube support and transport conveyor means is disposed to pass into the inlet opening and out of the outlet opening of the annealing chamber. The width of the tube support and transport means is about equal to the body portion of the tube disposed thereon, with the shoulder portion end of the tube extending beyond one side of the conveyor means. A heat source is disposed within the annealing chamber for maintaining a uniform high temperature within the chamber. A plurality .of combustion flame burners are disposed within the chamber along the path of travel of the conveyor means, which burners are disposed to direct the flames emanating therefrom upon the shoulder portion of the tubes disposed upon the conveyor means, whereby the tubes are rapidly brought to the annealing temperature.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS The tube annealing system shown schematicallyin FIG. 1 comprises; the annealing furnace I which has an inlet opening 11 at one end thereof, and an outlet opening I2 at the other end thereof. An endless chain conveyor 13 is disposed to pass through the annealing furnace I0 with the return path being beneath the furnace. Tube support means M are provided on the conveyor I3 and more particularly comprise a plurality of inverted V-shaped supports ISywith the apex of the V transverse to the direction of travel of the conveyor so that tube troughs I6 are formed between adjacent inverted V-shaped supports I5. The inverted V-shaped supports are formed of high temperature resistant metal plates with a plurality of apertures I7 therethrough. Plate burners I8 are disposed within the furnace I0 beneath the conveyor means 13. The plate burners I8 are gas fired and serve to heat the V-shaped supports I5, which have apertures I7 therein whereby the tubes 19 disposedthereon are also heated with a relatively uniform temperature being maintained within the annealing furnace 10. The tubes I9 comprise a relatively uniform diameter body portion 20 which has a uniform very thin wall thickness, for example of the order of about 0.003 to 0.005 inch, and a tapered shoulder portion 211 at one end of the body portion 20. The tapered shoulder portion 21 has a relatively thickened wall, for example about 0.015 to 0.035 inches thick.

A tube feed conveyor means 22 moves the tubes to indexing means 23, which deposits the tubes I9 upon the horizontal annealing conveyor I3 in a tube trough I16. The indexing means 23 also serves to position the tube properly upon the annealing conveyor, with the shoulder portion of the tube projecting beyond the side of'the inverted V-shaped supports I5 toward the shoulder burners 24. The individual shoulder burners 24! are connected to a gas supply manifold 25.

I The tubes are loaded onto the annealing conveyor I3 from a tube conveyor 22 which deposits the tubes 19 within the tube troughs I6 formed by the V-shaped supports 15. The body portion 20 of tubes I9 fits into troughs In, with the shoulder portion ZI extending beyond the edge of the V-shaped supports IS. The plurality of combustion flame shoulder burners 2d are disposed from the side wall of the annealing furnace III on the same side of the conveyor 13 from which the shoulder portions 2I extend. The shoulder burners 24 are disposed to direct the flame emanating therefrom upon the tapered shoulder portion 21 of respective tubes which are passed through the annealing furnace It). The tubes passing out the outlet opening I2 from the annealing furnace II) are deposited into tube holding means 26 mounted upon a cooling tower conveyor 27, which circulates the tubes within the cooling structure 28 to'permit determination of the temperature of the tubes before advancing the tubes onto the discharge conveyor 29 which brings the tubes to the next processing station. The structure of the annealing furnace I0 can be seen in greater detail in FIG. 3 wherein the furnace I0 comprises an outer frame 30, inner frame M which includes a refractory block upper portion 32, which permits combusted gas to pass slowly upward and out the stack 33. Support means 34 is provided for the conveyor I3, and drive means 35, for the conveyor 13, is generally indicated. 7

The invention can be best understood by reference to a specific exemplary embodiment wherein the tubes I9 are formed of aluminum with a body portion of about nine inches long with a diameter of about 1%. inch, a wall thickness of about 3 thousandths of an inch, and wherein the shoulder portions extends for about 1V2 inches. The shoulder portion has a wall thickness of about 0.030 in. The plate burners 1% heat the high temperature resistant V-shaped supports I5 to a high tem perature which permits maintenance of a uniform temperature distribution along the length of the tubes to insure against rupture and deformation of the thinwalled body portion when the shoulder portion is directly heated by the flames from the gas shoulder burners. The flame temperature of the combusted gas at the point where the flames from the shoulder burners impinge the tapered shoulder portion are about 2,400 to 2,600F.. The flame is preferably directed upon the underside of the tapered shoulder portion. For an annealing furnace which is about 35 inches long, preferably 17 shoulder burners are employed with the first 1 l burners starting at the inlet opening being spaced about 1% inch apart, and with the remaining six burners spaced about 2% inches apart.

It is possible utilizing the apparatus and method of the present invention to anneal the aluminum tubes described in about seconds. This is a significant reduction in annealing time from the several minutes previously required, and yet the annealing is carried out without destructive rupturing of the very thin-walled tube and without deformation of the tube also.

The temperature of the tubes upon entering the furnace is about 100F., and in passing through the furnace is about 15 seconds, the temperature of the tubes is raised to about 960F., well above the annealing temperature of the aluminum which is at least about 850F.

In summary, the present invention permits the rapid annealing of work hardened thin-wall tubes, to provide a soft, workable squeeze tube. Vast numbers of tubes must be so annealed, and the time saving had from the present invention is significant. The annealing is carried out rapidly without deformation or damage to the tubes.

The flame from the shoulder burners as can be seen in FIG. 3 is directed in the same horizontal plane in which the tubes are disposed, with the flame impinging the shoulder portion of the tube as the tube passes through the flame. The movement of the tube through the flame means that the flame is not directed continuously on one portion of the tube shoulder.

The spacing of the shoulder burners results in a succession of rapid heating periods when the flame impinges the moving tube, and conductive heating periods between burners during which the temperature of the tube tends to equalize. The shoulder burners can be more widely spaced at the exit end of the furnace because the tubes have already been raised to the proper annealing temperature, with the latter burners just maintaining the tubes at this temperature.

I claim:

1. Method of annealing thin-walled metal tubular members which comprise a body portion and a tapered shoulder portion at one end thereof said tapered shoulder portion having a relatively thicker wall comprising:

a. disposing the tubular member upon a hot conductive heating surface, with the shoulder portion extending beyond the heating surface, whereby the body portion is conductively heated; and

b. directing a combustion flame upon the shoulder portion of the tubular member to rapidly heat the tubular member to the annealing temperature of the metal to thereby anneal the metal tubular memher.

2. The method specified in claim 1, wherein the combustion flame is directed upon the shoulder portion of the tubular member during a portion of the time the tubular member is disposed within a heating chamber.

3. The method specified in claim 1, wherein the metal is aluminum which has been work hardened by impact forming of the tubular member and which is annealed to the soft state by heating the tubular member to at least about 850F.

4. The method specified in claim 1, wherein the conductive heating surface comprises a supporting conveyor which is passed through an annealing furnace with the tubular members supported thereon.

5. The method specified in claim 1, wherein the tubes are moved by the conveyor means past a plurality of spaced burners whereby the flames from the burners impinge the shoulder portion of the tube as the tube moves past the spaced burners. 

2. The method specified in claim 1, wherein the combustion flame is directed upon the shoulder portion of the tubular member during a portion of the time the tubular member is disposed within a heating chamber.
 3. The method specified in claim 1, wherein the metal is aluminum which has been work hardened by impact forming of the tubular member and which is annealed to the soft state by heating the tubular member to at least about 850*F.
 4. The method specified in claim 1, wherein the conductive heating surface comprises a supporting conveyor which is passed through an annealing furnace with the tubular members supported thereon.
 5. The method specified in claim 1, wherein the tubes are moved by the conveyor means past a plurality of spaced burners whereby the flames from the burners impinge the shoulder portion of the tube as the tube moves past the spaced burners. 